Effects of the time intervals between venipuncture and serum preparation for serum peptidome analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Fucosylated C4b-binding protein α-chain, a novel serum biomarker that predicts lymph node metastasis in pancreatic ductal adenocarcinoma

C4b-binding protein α-chain (C4BPA) was previously identified as a novel serum biomarker for pancreatic ductal adenocarcinoma (PDAC). To apply this biomarker for clinical diagnosis, a lectin ELISA was established to measure serum fucosylated (Fuc)-C4BPA levels in 45 patients with PDAC, 20 patients with chronic pancreatitis (CP) and 50 healthy volunteers (HVs) in one training and three validation sets. The lecithin ELISA developed in the current study exhibited satisfactory within-run (2.6–6.7%) and between-day (1.8–3.6%) coefficient of variations. Serum Fuc-C4BPA levels in patients with PDAC (0.54±0.27 AU/ml) was significantly higher than that in HVs (0.21±0.06 AU/ml; P<0.0001) and patients with CP (0.25±0.03 AU/ml; P<0.0001). Additionally, serum Fuc-C4BPA levels in preoperative patients were significantly decreased compared with postoperative patient sera (P<0.0003). The receiver operating characteristic (ROC) curve analyses revealed that the area under the curve (AUC) of Fuc-C4BPA (0.985) was higher than that of carbohydrate antigen (CA)19-9 (0.843), carcinoembryonic antigen (0.548) and total C4BPA (0.875) (P<0.001). To analyze the clinical significance of Fuc-C4BPA, the ability of Fuc-C4BPA to predict lymph node metastasis was compared with that of CA19-9. The AUC of serum Fuc-C4BPA levels (0.703) was significantly higher than that of serum CA19-9 levels (0.500) in patients with PDAC (P<0.001). The current study established a novel lectin ELISA for measuring serum Fuc-C4BPA levels. Thus, Fuc-C4BPA has potential clinical applications owing to its high diagnostic value in PDAC.

The Influence of Blood Collection Tubes in Biomarkers' Screening by Mass Spectrometry

PURPOSE

Mass spectrometry is one of the rapidly developing bio-analytical techniques in recent years, and it shows that the results of biomarkers' screening can be influenced by pre-analytical process. The selection of the blood collection tubes is one of the most significant steps of pre-analytical process which is often neglected by researchers. So, it is urgent to define the influence of blood collection tubes clearly in biomarkers' screening.

EXPERIMENTAL DESIGN

Two types of blood collection tubes, non-additive tubes and coagulant activator tubes, are used to collect serum samples from patients and healthy controls. All samples are analyzed using matrix-assisted laser desorption ionization-time of flight mass spectrum in this study.

RESULTS

The serum protein profile changes while using coagulant tubes whether for patients or healthy controls. It is found that the effect of coagulant on serum protein of patients is smaller than that of control group. There are 27 significantly different peaks between the control group and the control coagulant group. However, between patient group and patient coagulant group, only one differential peak is obtained. Coagulant changes the expression differences between patients and healthy controls, making the differences expand, shrink or reverse, and most of the polypeptides are small molecule, which will change the results of biomarker's screening.

CONCLUSIONS AND CLINICAL RELEVANCE

This research suggested that different types of blood collection tubes would influence the final laboratory results. So it's important for clinicians to choose the proper tubes to detect biomarkers and make correct diagnoses.

Assessment by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry of the Effects of Preanalytical Variables on Serum Peptidome Profiles Following Long-Term Sample Storage

PURPOSE

Human serum and plasma are often used as clinical specimens in proteomics analyses, and peptidome profiling of human serum is a promising tool for identifying novel disease-associated biomarkers. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is widely used for peptidomic biomarker discovery. Careful sample collection and handling are required as either can have a profound impact on serum peptidome patterns, yet the effects of preanalytical variables on serum peptidome profiles have not been completely elucidated. The present study investigated the effects of preanalytical variables, including storage temperature, duration (up to 12 months), and thawing methods, on MALDI-TOF MS-based serum peptidome patterns.

EXPERIMENTAL DESIGN

Aliquots of serum samples were pretreated with weak cation exchanger magnetic beads using an automated ClinProtRobot system and then analyzed by MALDI-TOF MS.

RESULTS

A number of significant differences in peak intensities were observed depending on sample processing variables.

CONCLUSIONS AND CLINICAL RELEVANCE

These peaks can be used as sample quality markers to assess the effects of long-term storage on serum peptidome profiles using MALDI-TOF MS.

The Impact of Pre-Analytical Conditions on Human Serum Peptidome Profiling

The successful use of proteomic technology for the discovery of clinically relevant, new candidate biomarkers, especially in the low molecular weight range (peptidome), calls for a careful consideration of standardized operating procedures (SOP) for pre-analytical variables, including samples handling and storage. The current lack of standardization, widely considered a relevant source of random and systematic errors, underlies the uncertainty of analytical results and poor comparability, especially in multi-centric or inter-laboratory studies. In their recent study, Tsuchida et al. used the MALDI-TOF/MS technique to investigate the effect of long-term storage at -20 °C, -80 °C, and in liquid nitrogen on serum samples obtained for peptidomic analyses. The authors have also evaluated the effects of different sample thawing modalities. By including results from the same series as that reported on in a previous publication, they have effectively defined some important requirements for the peptidomic analysis of serum samples (e.g., maximum time intervals between venepuncture and serum separation [1 h], minimum temperature for long-term sera storage temperature [-80 °C], ideal conditions for sample thawing).

Development of a sandwich ELISA for the thrombin light chain identified by serum proteome analysis

We previously identified novel biomarker candidates in biliary tract cancer (BTC) using serum proteome analysis. Among several candidates, we focused on thrombin light chain which is a 4204 Da peptide as the most promising biomarker for BTC. To move thrombin light chain toward potential diagnostic use, we developed an enzyme immunoassay that enables to measure serum thrombin light chain levels.

Both one monoclonal antibody specific to the N-termini and one polyclonal antibody were used to develop a sandwich ELISA for thrombin light chain. The assay was evaluated by comparing the results with those obtained by the ClinProt™ system. Serum samples were obtained from 20 patients with BTC, 20 patients with BBTDs and 20 HVs using the ClinProt™ system and ELISA.

The results of the established ELISA showed a positive correlation with the findings by ClinProt™ system (slope=0.3386, intercept=34.901, r²=0.9641). The performance of the ELISA was satisfactory in terms of recovery (97.9–102.5%) and within-run (1.5–4.8%) and between-day (1.9–6.7%) reproducibility. Serum thrombin light chain levels were significantly greater in BTC (176.5±47.2 ng/mL) than in BBTDs (128.6±17.4 ng/mL) and HVs (127.6±16.0 ng/mL) (p<0.001).

The sandwich ELISA developed in this study will be useful for validation of the diagnostic significance of serum thrombin light chain levels in various cancers.

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We previously identified novel biomarker candidates in biliary tract cancer (BTC) using serum proteome analysis. Among several candidates, we focused on thrombin light chain which is a 4204 Da peptide as the most promising biomarker for BTC.

•

Both one monoclonal antibody specific to the N-termini and one polyclonal antibody were used to develop a sandwich ELISA for thrombin light chain.

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The performance of the ELISA was satisfactory in terms of recovery (97.9–102.5%) and within-run (1.5–4.8%) and between-day (1.9–6.7%) reproducibility.

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Serum thrombin light chain levels were significantly greater in BTC (176.5±47.2 ng/mL) than in BBTDs (128.6±17.4 ng/mL) and HVs (127.6±16.0 ng/mL) (p<0.001).

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The sandwich ELISA developed in this study will be useful for validation of the diagnostic significance of serum thrombin light chain levels in various cancers.

Systematic evaluation of immune regulation and modulation

Cancer immunotherapies are showing promising clinical results in a variety of malignancies. Monitoring the immune as well as the tumor response following these therapies has led to significant advancements in the field. Moreover, the identification and assessment of both predictive and prognostic biomarkers has become a key component to advancing these therapies. Thus, it is critical to develop systematic approaches to monitor the immune response and to interpret the data obtained from these assays. In order to address these issues and make recommendations to the field, the Society for Immunotherapy of Cancer reconvened the Immune Biomarkers Task Force. As a part of this Task Force, Working Group 3 (WG3) consisting of multidisciplinary experts from industry, academia, and government focused on the systematic assessment of immune regulation and modulation. In this review, the tumor microenvironment, microbiome, bone marrow, and adoptively transferred T cells will be used as examples to discuss the type and timing of sample collection. In addition, potential types of measurements, assays, and analyses will be discussed for each sample. Specifically, these recommendations will focus on the unique collection and assay requirements for the analysis of various samples as well as the high-throughput assays to evaluate potential biomarkers.

Fibrinogen alpha C chain 5.9 kDa fragment (FIC5.9), a biomarker for various pathological conditions, is produced in post-blood collection by fibrinolysis and coagulation factors

BACKGROUND

Fibrinogen alpha C chain 5.9 kDa fragment (FIC5.9) is a new serum biomarker for chronic hepatitis that was discovered by proteomics analysis. Previous studies have shown that FIC5.9 is derived from the C-terminal region of fibrinogen alpha chain and the serum levels of FIC5.9 decrease in chronic hepatitis. It also have been reported that FIC5.9 cannot be detected in the blood stream of the systemic circulation and it is released from fibrinogen during blood clotting in collecting tube. However, the mechanism of FIC5.9 releasing from fibrinogen is unclear.

METHODS

We formulated a hypothesis that FIC5.9 is released by enzymes that are activated by post-blood collection and may be coagulation and fibrinolysis factors. In this study, we analyzed the mechanisms of FIC5.9 releasing from fibrinogen in healthy blood.

RESULTS

Our analysis showed that thrombin acts as an initiator for FIC5.9 releasing, and that mainly plasmin cleaves N-terminal end of FIC5.9 and neutrophil elastase cleave C-terminal end of FIC5.9.

CONCLUSION

FIC5.9 reflects minute changes in coagulation and fibrinolysis factors and may be associated with pathological conditions.

Increased concentrations of apo A-I and apo A-II fragments in the serum of patients with hepatocellular carcinoma by magnetic beads-assisted MALDI-TOF mass spectrometry

OBJECTIVES

Recent advances in sophisticated technologies in proteomics should provide promising ways to discover novel markers for hepatocellular carcinoma (HCC) in the early diagnosis.

METHODS

Serum peptide and protein profiling was conducted by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Profiling was carried out in a training set of 16 patients with HCC and a testing set of 15 patients with cirrhosis without HCC. All the patients were hepatitis C virus positive. Candidate peaks were processed to partial purification, followed by protein identification by amino acid sequence analysis. Immunoprecipitation was conducted to confirm the protein identity.

RESULTS

Partial purification and protein identification revealed that one peak that was up-regulated in HCC sera both in the training and the testing sets was a fragment of apolipoprotein A-I (apo A-I). Immunoprecipitation confirmed this result.

CONCLUSIONS

MALDI-TOF MS analysis revealed that apo A-I is a potential novel serum marker of HCC. Combination of these pretreatments and the current magnet bead-assisted MALDI-TOF MS will further enhance the efficiency of biomarker discovery for HCC.

MS-based monitoring of proteolytic decay of synthetic reporter peptides for quality control of plasma and serum specimens

OBJECTIVES

To determine the preanalytical quality of serum and plasma by monitoring the time-dependent ex vivo decay of a synthetic reporter peptide (RP) with liquid chromatography/mass spectrometry (LC/MS).

METHODS

Serum and plasma specimens were spiked with the RP and proteolytic fragments were monitored with LC/MS at different preanalytical time points ranging from 2 to 24 hours after blood withdrawal.

RESULTS

The concentration of fragments changed in a time-dependent manner, and respective peptide profiles were used to classify specimens according to their preanalytical time span. Classification accuracy was high, with values always above 0.89 for areas under receiver operating characteristic curves.

CONCLUSIONS

This "proteomics degradation clock" can be used to estimate the preanalytical quality of serum and plasma and might have impact on quality control procedures of biobanking repositories.

Serum fibrinogen alpha C-chain 5.9 kDa fragment as a biomarker for early detection of hepatic fibrosis related to hepatitis C virus

PURPOSE

Clinical application of biomarker candidates discovered by proteomic analysis is challenging. The purpose of this study was to standardize preanalytical conditions for measurement of serum levels of fibrinogen alpha C-chain 5.9 kDa fragment (FIC 5.9) and to test the diagnostic value of this peptide for detection of early hepatic fibrosis in patients with hepatitis C virus (HCV)-related chronic hepatitis.

EXPERIMENTAL DESIGN

Serum FIC 5.9 levels were measured by a sandwich ELISA. Effects on the serum FIC 5.9 level of temperature, the time between venipuncture and serum separation, and the types of collection tubes used were examined. The diagnostic value of serum FIC 5.9 as an early indicator of hepatic fibrosis due to HCV was then assessed.

RESULTS

FIC 5.9 was produced in a time- and temperature-dependent manner after venipuncture. Abnormal FIC 5.9 values were found in 89.5% of FI stage patients. Receiver operating characteristic analyses confirmed the superiority of FIC 5.9 over other conventional markers for early detection of fibrosis.

CONCLUSIONS AND CLINICAL RELEVANCE

The serum FIC 5.9 level may be an early indicator of hepatic fibrosis in HCV-related chronic liver diseases. This study provides an example of a pipeline from biomarker discovery by proteome analysis to assay optimization and preliminary clinical validation.

The application of a three-step serum proteome analysis for the discovery and identification of novel biomarkers of hepatocellular carcinoma

The representative tumor markers for HCC, AFP, and PIVKA-II are not satisfactory in terms of sensitivity and specificity in the early diagnosis of HCC. In search for novel markers for HCC, three-step proteome analyses were carried out in serum samples obtained from 12 patients with HCC and 10 with LC. As a first step, serum samples were subjected to antibody-based immunoaffinity column system that simultaneously removes twelve of abundant serum proteins. The concentrated flow-through was then fractionated using reversed-phase HPLC. Proteins obtained in each fraction were separated by SDS-PAGE. Serum samples obtained from patient with HCC and with LC were analyzed in parallel and their protein expression patterns were compared. A total of 83 protein bands were found to be upregulated in HCC serum. All the protein bands, the intensity of which was different between HCC and LC groups, were identified. Among them, clusterin was most significantly overexpressed (P = 0.023). The overexpression of serum clusterin was confirmed by ELISA using another validation set of HCC samples. Furthermore, serum clusterin was elevated in 40% of HCC cases in which both AFP and PIVKA-II were within their cut-off values. These results suggested that clusterin is a potential novel serum marker for HCC.

Identification of a Novel Biomarker for Biliary Tract Cancer Using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Early diagnosis of biliary tract cancer (BTC) is important for curative surgical resection. Current tumor markers of BTC are unsatisfactory in terms of sensitivity and specificity. In a search for novel biomarkers for BTC, serum samples obtained from 62 patients with BTC were compared with those from patients with benign biliary diseases and from healthy controls, using the MALDI-TOF/TOF ClinProt system. Initial screening and further validation identified a peak at 4204 Da with significantly greater intensity in the BTC samples. The 4204 Da peak was partially purified and identified as a fragment of prothrombin by amino acid sequencing. The sensitivity of the 4204 Da peptide for detection of stage I BTC cancer was greater than those for CEA and CA19-9. Also, serum levels of the 4204 Da peptide were above the cut-off level in 15 (79%) of 19 cases in which the CEA and CA19-9 levels were both within their cut-off values. Receiver operating characteristic analysis showed that the combination of the 4204 Da peptide and CA19-9 was significantly more sensitive for detection of stage I BTC cancer compared to CEA and CA19-9. These results suggest that this protein fragment may be a promising biomarker for biliary tract cancer.

Functional protease profiling for diagnosis of malignant disease

Clinical proteomic profiling by mass spectrometry (MS) aims at uncovering specific alterations within mass profiles of clinical specimens that are of diagnostic value for the detection and classification of various diseases including cancer. However, despite substantial progress in the field, the clinical proteomic profiling approaches have not matured into routine diagnostic applications so far. Their limitations are mainly related to high-abundance proteins and their complex processing by a multitude of endogenous proteases thus making rigorous standardization difficult. MS is biased towards the detection of low-molecular-weight peptides. Specifically, in serum specimens, the particular fragments of proteolytically degraded proteins are amenable to MS analysis. Proteases are known to be involved in tumour progression and tumour-specific proteases are released into the blood stream presumably as a result of invasive progression and metastasis. Thus, the determination of protease activity in clinical specimens from patients with malignant disease can offer diagnostic and also therapeutic options. The identification of specific substrates for tumour proteases in complex biological samples is challenging, but proteomic screens for proteases/substrate interactions are currently experiencing impressive progress. Such proteomic screens include peptide-based libraries, differential isotope labelling in combination with MS, quantitative degradomic analysis of proteolytically generated neo-N-termini, monitoring the degradation of exogenous reporter peptides with MS, and activity-based protein profiling. In the present article, we summarize and discuss the current status of proteomic techniques to identify tumour-specific protease-substrate interactions for functional protease profiling. Thereby, we focus on the potential diagnostic use of the respective approaches.

Identification of a high molecular weight kininogen fragment as a marker for early gastric cancer by serum proteome analysis

BACKGROUND

Serum biomarkers currently available for gastric cancers are not sufficiently sensitive and specific.

METHODS

We used matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MS) to generate comparative peptide profiles of serum samples obtained from gastric cancer patients (n = 81) and age- and sex-matched healthy controls (n = 66).

RESULTS

Because of initial screening and further validation, we found that the intensities of a 2209 m/z MS peak were increased in the preoperative sera obtained from gastric cancer patients, and we identified this peak, a 2209 Da peptide, as a high molecular weight (HMW) kininogen fragment. Receiver operating characteristic analyses showed that the area under the curve (AUC) for the 2209 Da peptide (AUC = 0.715) was greater than those for conventional tumor markers (carcinoembryonic antigen AUC = 0.593, carbohydrate antigen 19-9 AUC = 0.527) used for the detection of stage I gastric cancers. Inverse correlations were observed between the levels of intact HMW kininogen and the 2209 Da peptide, suggesting that the upregulation of some protease activities is responsible for the overproduction of a kininogen fragment in gastric cancer patients.

CONCLUSIONS

Serum levels of the 2209 Da peptide identified in this study have a greater diagnostic ability than those of conventional tumor markers used for the early detection of gastric cancer.

Identification of vitronectin as a novel serum marker for early breast cancer detection using a new proteomic approach

PURPOSE

Breast cancer is the most frequent malignancy in women. However, no useful serum markers with high sensitivity and specificity for the detection of early breast cancer have been identified. The search for biological markers of early breast cancer is of continual interest in experimental and clinical breast cancer research. We recently described a simple and highly reproducible three-step proteome analysis for identifying potential disease-marker candidates among the low-abundance serum proteins.

METHODS

Serum samples from breast ductal carcinoma in situ (DCIS) patients and normal controls were subjected to a three-step serum proteome analysis. The steps were the following: first, immunodepletion of most abundant proteins; second, fractionation using reverse-phase high-performance liquid chromatography; and third, separation using two-dimensional electrophoresis (2-DE). Differences revealed by protein staining were further confirmed by Western blotting, immunohistochemical staining, and enzyme-linked immunosorbent assays (ELISA).

RESULTS

Twenty-two upregulated and 26 downregulated spots were detected on the 2-DE gels, and a total of 33 proteins were identified by liquid chromatography and tandem mass spectrometry. Western blotting confirmed that the level of vitronectin was significantly increased in DCIS patients compared with that of normal controls. Immunohistochemical staining of vitronectin in breast cancer tissue revealed high expression in small vessel walls surrounding cancer cells and the extracellular matrix of stroma. Moreover, vitronectin serum concentrations, as measured by ELISA, were significantly increased in patients with DCIS or more advanced breast cancer compared with those of normal controls.

CONCLUSIONS

Vitronectin could serve as a promising serum marker for the detection of primary breast cancer.

Increased serum levels of pigment epithelium-derived factor by excessive alcohol consumption-detection and identification by a three-step serum proteome analysis

BACKGROUND

The search for biological markers of alcohol abuse is of continual interest in experimental and clinical alcohol research. We previously used gel-free proteome analysis methods such as the ProteinChip(®) system and the ClinProt™ system to search for new serum markers for alcoholism and found several novel marker candidates. As serum contains thousands of proteins and peptides that are present in a large dynamic concentration, depletion of the abundant proteins and further fractionation of the remainder is necessary to get into the deep proteome. We recently described a simple and highly reproducible three-step method for identifying potential disease-marker candidates among the low-abundance serum proteins.

METHODS

Two serum samples-one on admission and one after 8 weeks of abstinence-were obtained from 8 patients with alcohol dependency. The samples were subjected to a three-step serum proteome analysis. The steps were the following: first, immunodepletion of the 6 most abundant proteins; second, fractionation using reverse-phase high-performance liquid chromatography; and third, separation using one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Differences revealed by protein staining were further confirmed by Western blotting and by enzyme-linked immunosorbent assays (ELISA).

RESULTS

Three-step serum proteome analysis revealed that the serum levels of 5 proteins, alpha2-HS glycoprotein, apolipoprotein A-I, glutathione peroxidase 3, heparin cofactor II, and pigment epithelial-derived factor (PEDF), were significantly greater on admission than after 8 weeks of abstinence. We focused on PEDF because alterations in its levels in alcoholic subjects are not well known. Western blotting and ELISA confirmed the upregulation of PEDF. Serum PEDF levels were significantly greater in moderate to heavy habitual drinkers (14.2 ± 7.7 μg/ml) than in healthy subjects without a drinking history (5.5 ± 3.0 μg/ml) (p < 0.001). The serum PEDF levels in subjects with nonalcoholic chronic liver diseases were comparable to the PEDF levels in healthy subjects.

CONCLUSION

  Three-step serum proteome analysis reveals that excessive alcohol drinking increases the PEDF level.

Specific Investigation of Sample Handling Effects on Protease Activities and Absolute Serum Concentrations of Various Putative Peptidome Cancer Biomarkers

Introduction

In the search for novel cancer biomarkers, various proteolytically derived peptides have been proposed to exhibit cancer or cancer-type specificity. As these peptides are presumably also generated after sample collection by tumor-specific proteases, extensive investigation of the involved proteolytic processes is crucial for further research.

Materials and Methods

Using two previously developed and fully validated liquid-chromatography coupled to tandem-mass spectrometry assays, absolute quantification of, in total, 13 proteolytically derived peptides in human serum was accomplished. The analytes included eight peptides derived from inter-α-trypsin inhibitor heavy chain-4 (ITIH₄-30, ITIH₄-29, ITIH₄-28, ITIH₄-27, ITIH₄-26, ITIH₄-25, ITIH₄-22, and ITIH₄-21), bradykinin, des-Arg⁹-bradykinin, Hyp³-bradykinin, and fragments from fibrinogen-α-chain (Fib-α _[605–629]) and complement component 4a (C4a _{[1337–1350]}). Samples were obtained from different healthy individuals and prepared with variable tube types, clotting times, and temperatures. Furthermore, stabilities in the serum fraction were assessed and compared to stabilities in serum from breast cancer patients.

Results and Discussion

The quantitative analyses showed either increasing or decreasing serum concentrations during blood coagulation, while comparable effects were observed in serum separated from the blood clot. Furthermore, comparisons of inter- and intra-individual variations suggested better reflection of an individual’s protease activity after prolonged ex vivo incubation. This was illustrated for the putative breast cancer marker ITIH₄-22, revealing better differentiation after incubation of serum at ambient temperature for 24 h.

Conclusion

The presented study provides suggestions for more specific and optimized sample preparation, as well as extended knowledge necessary to further explore the opportunities of these proteolytic peptides as cancer biomarkers.

Potential biomarkers for esophageal carcinoma detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

BACKGROUND

Currently, no satisfactory biomarkers are available to screen for esophageal squamous cell carcinoma (ESCC). The goal of this study was to find biomarkers and establish a serum protein fingerprint model for early diagnosis of ESCC using the ClinProt protocol of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

METHODS

Serum samples were collected from 62 patients with ESCC, nine patients with esophageal adenocarcinoma (EA) and 38 healthy individuals. Proteomic spectra of mass to charge ratio (m/z) were generated following the application of plasma to weak cationic-exchanger magnetic beads (WCX-MB). The spectral data were analyzed using a support vector machine, and potential biomarkers were chosen for system training and used to construct diagnostic models.

RESULTS

Three differential patterns were established using MALDI-TOF MS. Pattern 1, consisting of 11 protein peaks, separated ESCC patients from the healthy individuals with a sensitivity of 90.0% and a specificity of 88.4%. Pattern 2, consisting of eight protein peaks, separated ESCC in stage I and stage II from stage III and stage IV with a sensitivity of 92.9% and a specificity of 82.3%. Pattern 3, consisting of seven protein peaks, separated ESCC from EA with a sensitivity of 91.3% and a specificity of 80.0%.

CONCLUSIONS

These results suggested that MALDI-TOF MS combined with MB separation yields significantly higher sensitivity and specificity for the detection of serum protein in patients with ESCC.